1. Field of the Invention
The present invention relates generally to a method of manufacturing an integrated circuit, and more specifically to a method of manufacturing an integrated circuit feeding an overlay data of a layer to a next layer as an alignment data.
2. Description of the Prior Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion. Transferring of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network or adjacent target portions that are successively patterned with a lithographic apparatus, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction.
In order to monitor the lithographic process, it is necessary to measure parameters of the patterned substrate, for example the overlay error between successive layers formed in or on it. There are various techniques for making measurements of the microscopic structures formed in lithographic processes, including the use of scanning electron microscopes and various specialized tools. One form of specialized inspection tool is a scatterometer in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered or reflected beam are measured. By comparing the properties of the beam before and after it has been reflected or scattered by the substrate, the properties of the substrate can be determined. This can be done, for example, by comparing the reflected beam with data stored in a library of known measurements associated with known substrate properties. Two main types of scatterometer are known. Spectroscopic scatterometers direct a broadband radiation beam onto the substrate and measure the spectrum (intensity as a function of wavelength) of the radiation scattered into a particular narrow angular range. Angularly resolved scatterometers use a monochromatic radiation beam and measure the intensity of the scattered radiation as a function of angle.
Devices are built up layer by layer and overlay is a measure of a lithographic apparatus' ability to print these layers accurately on top of each other. Successive layers or multiple processes on the same layer must be accurately aligned to the previous layer, otherwise electrical contact between structures will be poor and the resulting devices will not perform to specification. Overlay is a measure of the accuracy of this alignment. Good overlay improves device yield and enables smaller product patterns to be printed. The overlay error between successive layers formed in or on the patterned substrate is controlled by various parts of the exposure apparatus (of the lithographic apparatus). It is mostly the alignment system of the lithographic apparatus that is responsible for the alignment of the radiation onto the correct portions of the substrate.
With the miniaturization of integrated circuits, it becomes a critical challenge to form a desired pattern as well as forming it on a specific position by a lithography process. Consequently, modern lithography apparatuses involve extensive measurement. These operations, being time-consuming, limit the throughput of the lithography apparatus, and consequently increase the unit cost of the semiconductor or other products, specifically as pattern features become smaller and overlay performance requirements become ever more demanding. Therefore, an improved method being time-saving, accurate measuring, simulating and correcting of patterns actually printed on a substrate is urged in current industry.